There are in the prior art many reports and results of studies of the nature of crystal growth by varying the rate of the crystal formation over time. Many of these prior art studies have been made with transparent specimen materials to enable an observer, with the aid of a microscope and various electronic and photographic or other display means, to study in some details the formation of crystals as the crystal forming material is passed through a constant temperature gradient G zone at a variable rate of velocity R from a heated area of constant temperature to a cooling area of constant temperature with the freezing zone lying directly under a microscope. The crystal growing material is in a molten state as it leaves the heated area and freezes as it enters the cooling area.
Such studies have particular importance in the field of metallurgy and specifically in metal and metal alloy casting processes.
For more detailed descriptions of these prior art studies reference is made to a publication entitled "Solidification", which is a collection of papers presented at a seminar of the American Society for Metals on Oct. 11-12, 1969 and published by the American Society for Metals in Metals Park, Ohio, and copyrighted in 1971, and another publication entitled "A Quantitative Study of Factors Influencing Lamellar Eutectic Morphology During Solidification" by WFS Kaukler of the Space Sciences Laboratory, NASA, at the George C. Marshall Space Flight Center, in Huntsville, Al., in November, 1981, and further identified as NASA TM-82451, both of which are incorporated herein by reference.
While these prior art studies have revealed much valuable information about the growth of crystals, many questions relating thereto remain unanswered.
It is a primary object of this invention to provide a new and novel process for visually observing and studying the growth of crystals under controllable variable conditions never done heretofor.
It is another object of the invention to provide a method of investigating crystal growth with a variable temperature gradient G which is controllable to maintain the freezing isotherm of the specimen material at a substantially constant, unmoving position which always lies under the objective lens of the fixed position microscope.
Another object of the invention is to provide a method and apparatus for investigating crystal growth in a transparent material with controllable variable temperature gradient G which is positionable to maintain the melting point isotherm of the transparent material at a substantially constant, unmoving position under a fixed position microscope while said transparent material is moving at a rate R in a transverse direction under the microscope at a controllable rate of speed.
Yet another object of the invention is to investigate crystal growth in a transparent material which is movable at a controllable, variable rate from a heated or melting zone to a cooling or freezing zone with the temperatures of the heating and cooling zones being variable in a controlled manner to create a variable temperature gradient at the freezing isotherm and to maintain the freezing or solidifying isotherm of the transparent material in a fixed position under the objective lens of a microscope.
Still another object of the invention is an improved and novel method and apparatus for studying crystal growth in a moving transparent material by varying the temperature gradient across the freezing point of the transparent material with said freezing point remaining in a fixed position relative to a fixed position observing means.